A power conversion device includes a plurality of filter capacitors connected in series and arranged at an input side, a plurality of transformers in one-to-one correspondence with the plurality of filter capacitors, and a plurality of power conversion circuits in one-to-one correspondence with the plurality of filter capacitors, using as an input voltage a voltage applied to the filter capacitors, converting a direct current voltage to an alternating current voltage, and outputting the alternating current voltage to an primary side of transformers. Differences may occur in the output voltages of the power conversion circuits. Due to the differences in the output voltages of the power conversion circuits, an output current of the power conversion device may increase and decrease, and overcurrent may occur.
A power supply device for applications such as arc welding, as disclosed in Patent Literature 1, suppresses imbalances between terminal voltages of input-side filter capacitors caused by output imbalances of inverters arranged at a primary side of transformers, conduction width imbalances of switching elements of the inverters, or the like. Specifically, in this power supply device, for each filter capacitor voltage between terminals is detected, a differential voltage is detected relative to a reference signal, and pulse timing is corrected so as to become narrow along the time axis when the voltage between terminals is low.
In a DC-DC converter disclosed in Patent Literature 2, unitary units are provided in n groups for a direct current power supply, each of the unitary units having a pair of transformers and a pair of conversion circuit units. In addition to connecting in series between the n groups a secondary side of one of the transformers occurring in the unitary unit, by connection of a secondary side of the other transformer in the unitary unit in series between the n groups, increase or decrease of an output current of the power conversion device is suppressed.